Cementitious material



lot. cowosmows,

comma R PLASTIC.

Patented May 4, 1937 UNITED STATES Exam! PATENT OFFICE CELIENTITIOUSMATERIAL Oarlisle K. Roos, Fort Dodge, Iowa, assignor to United StatesGypsum Company, Chicago, 111., a corporation of Illinois No Drawing.Application January 19, 1925, Serial No. 3,477

5 Claims. (Cl. 106-24) This invention relates to improvements inbuilding material and more particularly to the production ofcementitious material of a porous structure which is obtained by the useof confined gas as an aggregate, rather than gas as an expansive forceto distend the volume of the cementitious material during the settingprocess.

cementitious material and particularly calcined gypsum has been employedfor years as a finishing coat or covering for the interior walls ofbuildings, and has been molded into blocks to form partitions and tilesto form roofs and fioors, it has also been employed as a filler inpoured roofs and floors and as a core for plaster board and plasterwallboard, as well as having been employed in other forms and articles.Calcined gypsum on account of its non-conductive and fire resistingqualities has been a desirable product for the purposes above described.In wall coverings the calcined gypsum has been used with sand as anaggregate to give it body for the first coats and a. retarder to delaythe setting so that it may be properly applied and in other cases fiberand sawdust has been added as an aggregate in lieu of the heavy sandaggregate which reduces the weight of the finished product. In theformation of roofs, floors, tile, block and plaster board or wallboardthe addition of fiber or sawdust aggregate detracts from its fireresisting quality which is as desirable in these products as decreasingthe weight of the finished product.

To overcome this objection and produce such articles of calcined gypsumin which the weight is greatly reduced and in which the articles possessthe qualities of unadulterated set gypsum, certain chemicals or mineralshave been added to the dry calcined gypsum which will upon the additionof water evolve a gas causing the mixture to pufi out or expand involume and upon the setting of the gypsum will form a porous body sothat articles thus produced will be of less weight per volume and be asfire resisting and better insulating mediums than unadulterated setgypsum.

It is an object of this invention to produce a porous body of setcalcined gypsum without the use or addition of chemicals or gasproducing agents to the gypsum which react with the water to form anexpanded plastic mass to be molded or otherwise formed into the requiredshape of the article desired. lqpl i itend an inert foam is formedcomprising a plurality of minute bubbles or air the enveloping films ofwhich are so individual in mass form that these air bubbles are ineffect an aggregate and then as the calcined gypsum is being mixed withwater, in the same manner as ordinarily employed to form the desiredarticle, such inert aggregate of minute air bubbles is thoroughlyincorporated in the plastic mass during the mixing process.

The incorporation of the air or gas aggregate has the same effect uponreducing the density of the plastic mass as any other aggregate lighterin weight than the cementitious material itself and reduces density ofthe entire mass to give lighter weight per unit volume. Because the airor gas is so much lighter in weight than any solid aggregate thereduction in unit volume weights is correspondingly much greater and dueto the fact that the air or gas is so thoroughly confined in such atough film of film forming substance, the air or gas will remainconfined during the mixing process of cementitious solid and water andthus permit of the novel aggregate being incorporated therein. Anyamount of porosity desired can be produced and a definite size ofporosity can be maintained, because the tough filmed bubbles of air orgas maintain their identity until the gypsum has set, and the tough filmenvelope of the confined air or gas aggregate is replaced by a permanentset wall of cementitious material with the air or gas still confined.

This application is a continuation-in-part of my prior application Ser.No. 733,197, filed August 20, 1924, now U. S. Patent No. 2,017,022,which describes broadly the application of this principle of reducingthe weight of articles made from calcined gypsum by the incorporation ofalgam of minute ai 1 bubbles in e ni'alssand sp'ameair describestlE'i-"eiii'forcifig of the air bubble enveloping films by an inorganicstabilizer, such as calcined gypsum, before the foam is mixed with theplastic mass. This prior application describes the beingwhipped into afine grained form and stabilized by the addition of a relativelysmairquantity'of' calcined gypsum which reinfofdesthewalls of thebubbles to such an extent that'thibam might be preserved indefinitely.It also states that other reagents'such as gelatin, dextrin and gumarabic added to the foam will reinforce the walls of the bubbles andproduce a a a gypsum, is desirable, while in the formation To 'fil'as'ter' board and other articles subjected to the heat of a drying kiln toset a foam with air bubbles stabilized by or anic a ents is desiraBle.In molded a'rflcles", were no ex'ternal pressure is applied, the airbubble walls may be readily reinforced, as specifically described in mysaid prior application, by calcined gypsum or other inorganic agentwhich will harden and produce a rigid and more or less fragile wall, andfoam bubbles so stabilized will act satisfactorily in such articles butwhere external pressure is applied to air bubble foam and cementitiousmaterial mixture the best result is obtained by a foam in which thewalls of the air bubbles are tough and pliable.

In applying this invention to the manufacture of plaster wallboard suchas made on a continuous machine like that described in the Utzman Patent1,330,413, February 10, 1920, and afterwards dried in a drying kiln thefoam is produced and then deposited upon the mixing belt where thecalcined gypsum and water are mixed by the mixing fingers to form ahomogeneous mass to be deposited upon the bottom cover sheet of thewallboard as it advances thereunder. It is seen that the addition of aninert foam at this step in the process of making wallboard is treatingthe foam in the same manner as any other aggregate that may be desiredto be incorporated In-the body of the core of the wallboard. In thecourse of formation of plaster wallboard on machines similar to theabove referred to Utzman patent the plastic mass deposited on the bottomcover sheet is advanced between pressure rolls as the top cover sheet isapplied, the pressure so applied to the plastic mass collecting in frontof the rolls spreads it out to form a core between the top and bottomcover sheets of even thickness between the edges.

In such an application of this invention the first step is to prepare asolution capable of being converted into a foam by agitation. There areseveral types of reagents which will produce such a foaming solution ormixture such as solutions, mixtures, or emulsions of flotation oils,

various organic compounds similar to soap, saponin, soap bark albumens,licorice etc The eficiency of the above mentioned reagents of coursevaries considerably and it has been found that 5 a water solutioncontaining up to three percent to% y sma quantity of ela in, e n arabicor other organic COHOIH of wdered soa bark produces satisfactoryresfiis. ucfi a so l'uti'on'hf soap bark and water may be agitated orwhipped into a foam same manner as eggs or cream.

such as rice our or other farinaceous paste is added and stirred into itthoroughly. The addition of this colloidal agent reinforce the filmenveloping the air bubbles so that each one will the air bubblesincorporated in the plastic mass being tough and pliable not only remainintact during the mixing with the cementitious material and water butare not broken or changed in volume and the ag regate formation ismaintained in passing through the pressure rolls as the board is formed.The quantity of foam incorporated into the wet mass on the mixing beltwill of course determine its cellular structure, and this in turndetermines the bulk and weight of the finished product. The wallboardsso formed are quickly dried by passing through a drying kiln as they areremoved from the discharge end of the machine.

In such an application of this invention the foam is continuously mixed,stabilized and immediately incorporated into the plasticcore materialwhich is continuously deposited on the continuously moving cover sheetand immediately passed through the pressure rolls and the board soformed continuously cut and removed from the machine and immediatelyentered into the drying kilns from which it emerges the finished productso that but little time is consumed from the initial stabilization ofthe air bubble walls to the completion of the finished product and thetoughness and pliability of the air bubble walls is of more importanceand more necessary to such an article than the permanency of thepreservatives of the air bubble formation as is required in a slowsetting article.

What I claim is:

1. A composition of matter comprising a cementitious material having anaggregate of bubbles incorporated therein to increase its normal bulk,the walls of said bubbles being reinforced with a colloidal agent fromthe group comprising gelatin, gum arabic, farinaceous paste, rice flourand dextrin to render them tough and pliable.

2. The process of producing a porous cement which comprises firstforming a foam, stabilizing the same by the addition of a colloid toreinforce the walls of the bubbles constituting the foam therebyrendering said walls tough and pliable and the foam substantiallynon-collapsible, incorporating said foam as an aggregate in a plasticcement mixture, and then allowing the same to harden.

3. A composition of material comprising a cement and an aggregate ofbubbles having tough and pliable walls incorporated therein to increasethe normal bulk and to decrease the normal weight of the cement, saidbubbles resulting from a wet foam initially formed before being added tothe cement and to which foam a colloid has been added prior to itsincorporation with the cement to reinforce the walls enveloping the airbubbles with tough, pliable and substantially non-collapsing films.

4. The process of producing porous cement which comprises whipping anaqueous solution of a foaming agent into a foam or lather, preventingthe subsequent collapse of said foam by the addition thereto of a gummycolloidal stabilizing agent, and thereupon incorporating saidsubstantially non-collapsible foam into a slurry of a cementitioussubstance capable of setting.

5. The process of producing a moldable cementitious product whichcomprises forming a foam, then rendering the walls of the bubbles ofsaid foam tough and pliable by adding to said foam after formation acolloidal substance, and then mixing the foam with a cement.

CARLISIE K. R008.

